Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-01-16
1998-12-08
Szekely, Peter A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 45, 524 50, 524 55, C08L 128, C08L 308, C08L 500
Patent
active
058470310
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a polymer composition and in particular to absorbing materials mainly based on renewable raw materials. For this reason they are biodegradable in principle. Owing to the mainly native origin, the absorbents do not comprise residual monomers, or considerably lower amounts thereof, as compared with absorbers based on polyacrylate. The polymeric compositions and absorbers according to the present invention have a comparatively high absorption capacity and absorption rate for water and aqueous solutions, no tendency to gel blocking (gel blocking: on contact with water the outer layers of the absorber stick together and prevent further advancement of the liquid into the absorber), and they are mechanically stable (with respect to the separation into the individual components). In swollen condition they separate into individual particles; they are non-aqueous and have a very high gel stability. The present invention further relates to a process for their production and to their use as fiber, film, powder, or granular material for the absorption of water, aqueous solutions or aqueous dispersions and body fluids in hygiene articles, such as tampons or diapers, in animal hygiene articles, in technochemical products, for example, packaging materials, in particular for meat and fish, in culture pots, as well as in soil conditioning and as cable sheathings.
Most of the absorbing materials used today, also referred to as superabsorbers, which are capable of absorbing large amounts of liquid (water, urine) within a short period of time, primarily are slightly cross-linked polyacrylates; therefore they are not based on renewable raw materials and their biodegradability is comparatively insufficient or they are not biodegradable at all.
Endeavoring to build up superabsorbers of renewable raw materials, acrylic acid was grafted on polysaccharides, for example on corn starch, as is described in DE-C-2612846. However, only small amounts of polysaccharides (up to a maximum of 25%) may be used, otherwise the absorption properties will deteriorate to a considerable extent.
By incorporating polysaccharides into the polymerization gel of polyacrylates, as is described in DE-OS 40 29 591, 40 29 592, and 40 29 593, the polyacrylates can also only be replaced to the extent of a maximum of 25%, without resulting in a clear deterioration of the absorption capacity and other properties of the resulting superabsorbers, even if various auxiliary agents are added additionally, such as fibers and, for example, aluminum cross-linkers. The polysaccharides are considered to be fundamental elements for the absorbers to obtain biodegradable units.
DE-PS 3132976 describes the mixing of polyacrylic acid with polysaccharides in powdery form and in solution, wherein the shell of the absorber particles of the mixtures are cross-linked with aluminum cross-linking agents, such as Al(OH).sub.2 OOCCH.sub.3 * 1/3 H.sub.3 BO.sub.3. Thus, this process cannot provide superabsorbers consisting by more than 60% of renewable raw materials.
According to the processes described in the art, the polysaccharides do not contribute much to the absorption as an absorption component.
Various patent publications, such as DE-OS 26 34 539, describe the production of carboxymethylcellulose-absorbers, i.e., of materials which are biodegradable in principle, by cross-linking the carboxymethylcellulose with various cross-linking agents in aqueous system. However, these absorbers show severe gel blocking.
U.S. Pat. No. 4,959,341 describes the production of an absorber based on carboxymethylcellulose, which consists of a mixture of carboxymethylcellulose, cellulose fibers, a hydrophobic component, and Al(OH).sub.2 OOCCH.sub.3 * 1/3 H.sub.3 BO.sub.3 as cross-linking agent, with the aluminum cross-linking agent causing a cross-linkage of the carboxymethylcellulose during the liquid absorption. These absorbers have good absorption properties, however, show blocking phenomena. Additionally, these absorbers can easily be separated by mechanical stres
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Bruggemann Helmut
Gunther Uwe
Klimmek Helmut
Chemische Fabrik Stockhausen GmbH
Szekely Peter A.
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